Voltage sensor for high and medium voltage use and a method of making the same

ABSTRACT

A voltage sensor is disclosed for high and medium voltage use, wherein a voltage divider is arranged in a housing with external creepage distance enlarging ribs. To implement structures for creepage path enlargement to a sensor housing in a very effective and easy way, the voltage divider is arranged in a housing or in housing modules which is or are covered at least partly by at least one shrinking tube of insulating material such that the shrinking creepage enlarging structures are implemented at least at outer surface of the shrinking tube.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to European PatentApplication No. 14001838.3 filed in Europe on May 27, 2014, the entirecontent of which is hereby incorporated by reference in its entirety.

FIELD

The present disclosure relates to a voltage sensor for high and mediumvoltage use, and a method of making the same.

BACKGROUND INFORMATION

Known voltage sensors use an impedance divider cast in some insulationmaterial (epoxy or polyurethane) in order to withstand voltage stresseson MV or HV lines. This solution is expensive and involves investmentinto a complex mold for casting, such as when the requirement ofcreepage distance is of importance and ribs on the sensor body are usedto achieve given creepage distance, such as in FIG. 1.

SUMMARY

A voltage sensor for high and medium voltage use is disclosed,comprising: a voltage divider arranged in a housing or housing moduleswith external shrinking creepage distance enlarging structures; and thevoltage divider being arranged in the housing or in housing moduleswhich is or are covered at least partly by at least one shrinking tubeof insulating material such that the shrinking creepage distanceenlarging structures are implemented at least at an outer surface of theshrinking tube.

A method for producing a voltage sensor is disclosed, comprising:covering a tubelike solid housing in which a voltage divider of a sensoris placed, or an output cable of the voltage divider, by a flexible tubeof insulating cold shrink material with implemented ribs structures, adiameter or resulting diameter of the housing or the cable being largerthan an inner diameter of the flexible tube in an unextended state;extending the flexible tube in diameter by an extrusion device toposition it over the housing or the cable; removing the extension devicewhen the flexible tube is positioned over the housing or the cable; andshrinking the flexible tube close on a surface of the housing or thecable.

A method for producing a voltage sensor is disclosed, comprising:covering a tubelike solid housing in which a voltage divider of a sensoris placed, or an output cable of the voltage divider, by a flexible tubeof insulating warm shrink material with implemented rib structures, adiameter or resulting diameter of the housing or the cable being largerthan an inner diameter of the flexible tube in an unshrunken state;positioning the flexible tube over the housing or the cable; andshrinking the flexible tube under heat treatment close on a surface ofthe housing or the cable.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages disclosed herein will become apparent from thedescription of the exemplary embodiments when read in conjunction withthe drawings, wherein:

FIG. 1 shows a known exemplary cast voltage divider;

FIG. 2 a- 2 c show an exemplary voltage divider as disclosed herein;and:

FIG. 3 shows another exemplary embodiment of a voltage divider asdisclosed herein.

DETAILED DESCRIPTION

Structures for creepage distance enlargement are disclosed herein whichcan be used with a sensor housing in a very effective and easy way.

According to exemplary embodiments, the voltage divider can be arrangedin a housing or in housing modules which is or are covered at leastpartly by at least one shrinking tube of insulating material such thatthe shrinking creepage distance enlarging structures are implemented atleast at the outer surface of the shrinking tube.

In exemplary embodiments, a standard shrinking tube with sheds can beused, which is shrunken around a voltage divider module. This solutioncan provide significant cost saving in mold investments and reduction onsensor costs as well as significant reduction on manufacturing time ofsuch solution.

Exemplary embodiments can reduce manufacturing time and effort anddecrease production costs and investments needed for production. Byusing standard shrinking tube with sheds, which is shrunken around avoltage divider module, significant cost saving in mold investments andreduction in sensor costs as well as significant reduction onmanufacturing time of such solution can be realized as mentioned.

In an exemplary embodiment, the shrinking tube can be placed on thehousing of the voltage divider near the distal ends of the housing,and/or at least partly over an output cable of the voltage sensor. Anexemplary embodiment is to cover the definite transition area betweenthe housing and the output cable, in order to implement at that place acreepage distance enlargement.

In an exemplary embodiment, the voltage sensor is located within orsurrounded by shielding electrodes, which are arranged inside or outsidethe voltage divider housing.

In an exemplary embodiment, the voltage divider part is cast in simpleshape and the insulation is done by insulating material; e.g., epoxy,polyurethane or similar.

According to an exemplary embodiment, the insulating shrinking tube canbe provided as a cold shrink tube, by the use of insulating coldshrinking material.

Alternatively but also advantageous is that the insulating shrinkingtube can be provided as a warm shrink tube, by the use of insulatingwarm shrinking material.

So the same effect of implementing creepage distance enlargement can beplaced on a sensor's housing or cable, in both cases in a very simpleway of manufacture.

A voltage sensor with the features disclosed herein can, for example, beused for indoor use.

But the same advantages of using a voltage sensor with the featuresdisclosed herein can be realized in a sensor provided for outdoor use.

According to the voltage sensor construction disclosed herein,implementation of local creepage distance enlargement element structurescan be realized, and a simplified method for producing voltage sensorscan be realized. According to an exemplary method of manufacture, atubelike solid housing in which the voltage divider of the sensor isplaced, or an output cable of the voltage divider, is covered by aflexible tube of insulating cold shrink material with implemented ribstructures such that the diameter or resulting diameter of the aforesaidhousing or the aforesaid cable is bigger (i.e., larger) than the innerdiameter of the unextended flexible tube. The flexible tube can beextended in its diameter by an extending means (such as any suitableextension device structure or mechanism), in order to position it overthe housing or the cable, and these extending means can be removed whenthe flexible tube is positioned over the housing or the cable, so thatthe flexible tube shrinks close on the surface of the housing or thecable.

An alternative method for manufacture includes, for example, a tubelikesolid housing in which the voltage divider of the sensor is placed, oran output cable of the voltage divider, being covered by a flexible tubeof insulating warm shrink material with implemented rib structures. Thediameter or the resulting diameter of the aforesaid housing or theaforesaid cable is bigger (i.e., larger) than the inner diameter of theunshrunken flexible tube, and the flexible tube will be positioned overthe housing or the cable, and the flexible tube shrinks under heattreatment close on the surface of the housing or the cable.

As shown in FIG. 2 a, the design of a standard voltage divider isillustrated as having high voltage impedance 1 and low voltage impedance2. Depending on electrical design and electric field distribution, sucha voltage divider may also include high voltage electrode 3 and/or lowvoltage electrode 4. Such divider can be cast in some insulationmaterial as shown in FIG. 1 as state of the art.

The voltage divider can be of capacitive or resistive type, or acombination of both.

Exemplary embodiments disclosed herein can include a design of a voltagesensor which does not involve such a casting process to form the finalshape of the voltage sensor. Instead, it is proposed that voltagedivider internal parts shown in FIG. 2 a can be cast in a simpleinsulating tube 7 of FIG. 2 b or other shape of insulating material andthen the shrinking tube, forming the ribs/insulator sheds 8, is appliedon top as shown in FIG. 2 a. The shrinking tube may be applied using forexample, hot or cold shrinking tube technology. In order to cover theends of shrinking tube, upper 9 and lower 10 cups could be used ifneeded.

Depending on a final electric field distribution inside of the sensor,the upper 9 and lower 10 cups, if made of electrically conductivematerial, can replace the high voltage electrode 3 and/or low voltageelectrode 4.

Another exemplary embodiment to increase the creepage distance caninclude not using the shrinking tube 8 on a simple body, but to applythe shrinking tube with ribs on the output cable 12 instead as shown inFIG. 3. In this case the lower cup 10 should not be connected to theground potential.

It will be appreciated by those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. The presently disclosedembodiments are therefore considered in all respects to be illustrativeand not restricted. The scope of the invention is indicated by theappended claims rather than the foregoing description and all changesthat come within the meaning and range and equivalence thereof areintended to be embraced therein.

NUMBERING

-   1 High voltage impedance-   2 Low voltage impedance-   3 High voltage electrode-   4 Low voltage electrode-   5 Cable-   6 Cable-   7 Insulating tube-   8 Ribs/insulator sheds-   9 Upper cup-   10 Lower cup-   11 Primary terminal to which the voltage to be measured is    connected/applied-   12 Output cable

1. A voltage sensor for high and medium voltage use, comprising: a voltage divider arranged in a housing or housing modules with shrinking creepage distance enlarging structures; and the voltage divider being arranged in the housing or in housing modules which is or are covered at least partly by at least one shrinking tube of insulating material such that the shrinking creepage distance enlarging structures are implemented at least at an outer surface of the shrinking tube.
 2. The voltage sensor according to claim 1, wherein the shrinking tube is placed on the housing of the voltage divider near distal ends of the housing, at least partly over an output cable of the voltage sensor.
 3. The voltage sensor according to claim 1, wherein the voltage sensor is located within or surrounded by shielding electrodes, which are arranged inside or outside the voltage divider housing.
 4. The voltage sensor according to claim 1, wherein the voltage divider part is a cast shape and the insulation includes insulating material.
 5. The voltage sensor according to claim 1, wherein the insulating shrinking tube is a cold shrink tube of insulating cold shrinking material.
 6. The voltage sensor according to claim 1, wherein the insulating shrinking tube is a warm shrink tube of insulating warm shrinking material.
 7. The voltage sensor according to claim 1, configured for indoor use.
 8. The voltage sensor according to claim 1, configured for outdoor use.
 9. A method for producing a voltage sensor, comprising: covering a tubelike solid housing in which a voltage divider of a sensor is placed, or an output cable of the voltage divider, by a flexible tube of insulating cold shrink material with implemented rib structures, a diameter or resulting diameter of the housing or the cable being larger than an inner diameter of the flexible tube in an unextended state; extending the flexible tube in diameter by an extension device to position it over the housing or the cable; removing the extension device when the flexible tube is positioned over the housing or the cable; and shrinking the flexible tube close on a surface of the housing or the cable.
 10. A method for producing a voltage sensor, comprising: covering a tubelike solid housing in which a voltage divider of a sensor is placed, or an output cable of the voltage divider, by a flexible tube of insulating warm shrink material with implemented rib structures, a diameter or resulting diameter of the housing or the cable being larger than an inner diameter of the flexible tube in an unshrunken state; positioning the flexible tube over the housing or the cable; and shrinking the flexible tube under heat treatment close on a surface of the housing or the cable.
 11. The voltage sensor according to claim 1, wherein the voltage divider part is a cast shape and the insulation includes epoxy or polyurethane.
 12. The voltage sensor according to claim 2, wherein the voltage sensor is located within or surrounded by shielding electrodes, which are arranged inside or outside the voltage divider housing.
 13. The voltage sensor according to claim 12, wherein the voltage divider part is a cast shape and the insulation includes insulating material.
 14. The voltage sensor according to claim 13, wherein the insulating shrinking tube is a cold shrink tube of insulating cold shrinking material.
 15. The voltage sensor according to claim 13, wherein the insulating shrinking tube is a warm shrink tube of insulating warm shrinking material.
 16. The voltage sensor according to claim 15, configured for indoor use.
 17. The voltage sensor according to claim 16, configured for outdoor use. 